Question

Although both $CO_2$ and $H_2O$ are triatomic molecules, the shape of $H_2O$ molecule is bent while that of $CO_2$ is linear. Explain this on the basis of dipole moment.

Answer 1

According to experimental results, the dipole moment of carbon dioxide is zero. This is possible only if the molecule is linear so that the dipole moments of $C-O$ bonds are equal and opposite to nullify each other.

Resultant $\mu$ = $0 D$
$H_2O$, on the other hand, has a dipole moment value of $1.84 \;D$ (though it is a triatomic molecule as $CO_2$). The value of the dipole moment suggests that the structure of $H_2O$ molecule is bent where the dipole moment of $O-H$ bonds are unequal.